Seems to me that the definition of 'organised crime' is obvious, and clear and just has to be generally accepted-----it's ORGANISED (British spelling).
I think the answer to your question is complex and requires more than a short post. You can find some thoughts on why it is so difficult to define organized crime as well as references to relevant literature in chapters 1&2 of my book "Organized Crime: Analyzing illegal activities, criminal structures, and extra-legal governance" (2016).
Re-reading Klaus's wonderful book. The most comprehensive summary of the literature by far. Together with clear expositions. The issue comes sharply into focus when we discuss "mafias" with "organised crime." Is organized crime really another term for mafias? Which seems sometimes the case. Yet we know from Gambetta and others that mafias are a specific and definable type of illegal enterprise. Where does that leave organized crime?